Integrated optical devices are known to be used in communication networks employing optical radiation for information transmission. An example of integrated optical devices is the integrated optical waveguides by means of which optical paths are implemented for processing optical radiation.
Integrated optical waveguides are known to be defined by a core that is arranged on a reference substrate and surrounded by a coating or cladding. The core has a relatively high index of refraction, while the coating has an index of refraction which is lower than that of the core, so that the optical radiation is essentially confined within the optical path as represented by the waveguide core.
The need is also known to develop integrated optical devices in which the optical radiation propagating inside a waveguide can be provided to optoelectronic devices, such as, for example, photodetectors. Furthermore, it is typically required the provision of optical devices suitable to process the optical radiation they receive from other optoelectronic devices, such as, for example, photodiodes or light sources in general.
In order to meet these needs, integrated optical devices are known to be manufactured provided with a reflecting surface (also known as a turning mirror) that is suitable to turn the optical radiation coming from a waveguide integrated in the optical device to optoelectronic devices. A reflecting surface of this type is further suitable to turn the optical radiation coming from an optoelectronic device to the integrated waveguide.
U.S. Pat. No. 5,135,605 proposes a process for manufacturing an integrated optical device composed of a waveguide, the core of which ends in the proximity of a recess which is provided with a sloped wall facing a wall adjacent to the termination of the waveguide. The sloped wall has a slope of about 45° relative to the direction of waveguide propagation, and a turning mirror is obtained thereon in order to turn the optical radiation upwardly. In the above-mentioned patent, it is stated that the wall adjacent to the waveguide termination results to be “almost” vertical relative to the direction of propagation in the waveguide, and this allows minimizing the optical radiation refraction upon passing through the wall in the direction of the waveguide. However, it should be noticed that the Figures annexed to U.S. Pat. No. 5,135,605 highlight that the manufacturing process described therein provides for an etching step by means of which a wall can be obtained that is in any case, differently from what has been stated, sloped relative to the direction of the waveguide, and has even a quite round profile. For these reasons, it is presumable that the residual losses that are due to the optical radiation refraction which, upon passing through such wall, either enters or comes out from the recess along the direction of the waveguide are still found.